Nothing can sideline you from your workout routine faster than knee pain.

But one of the most common ways to treat it might not be helping much at all, new research published in JAMA finds.

In the study, 70 people with symptomatic knee arthritis received steroid injections in their knees every 12 weeks for two years, while 70 others with the same condition were given placebo shots with just saline.

The researchers discovered that the steroid shots didn’t improve pain ratings any more than the sham treatment did—but they did cause greater cartilage loss in the knees over the two-year study.

That could be a problem, the researchers say.

While the study didn’t show any worsening of symptoms due to the cartilage loss, it’s possible that deterioration would be more evident in longer-term studies.

In fact, greater cartilage loss has been linked to higher rates of arthroplasty, a surgical procedure that restores the function of a joint wrecked by arthritis.

Prior studies have supported corticosteroid injection for knee arthritis, under the belief that it reduced inflammation and thus could reduce pain and protect against cartilage loss.

But these studies didn’t use a sham injection, and that’s a problem, since any kind of shots come with a strong placebo benefit, the researchers say.

Want to protect your joints? Check out the 4 ways young guys are wrecking their knees—and how to save them instead.

In the meantime, load up your plate with fiber.

A fiber-rich diet can stop knee pain from worsening, as we recently reported.